Similar, l had been a middle and Index finger player for years. Then I started having problems with my middle finger locking up.Our slide guitar player likes the contrast between the slide's smooth dynamics and the punch/stab of slap bass, so he likes for me to throw some of that in when he's taking a lead or singing or something. It gives some punch to what he's doing.
Actually, my first experience playing slap was because, early on in my playing, I'd get blisters on my plucking fingers. Slapping with my thumb was a way to give my fingers a break. Of course I didn't develop any fluency or fluidity at this stage, it was more necessity than anything.
At that point I decided, for the sake of longevity, to learn to play with every technique I could think of.
One finger with wrist action, all thumb, slap, pick.
It has served me well the past 20 years, with no locking of my fingers since. It comes in handy on nights when my right hand is tight as well.